Remove unwanted gFTMutex from DirectWrite port.

This mutex exists because this file started life as a copy of the
FreeType port. There is no global library state to protect here,
so there is no need for the mutex.

R=caryclark@google.com

Review URL: https://codereview.chromium.org/80983003

git-svn-id: http://skia.googlecode.com/svn/trunk@12353 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed